1. Field of the Invention
This invention relates to a stand apparatus, in which heavy "medical optical devices" such as an operating microscope and its auxiliary devices are supported at the front end portion of a retaining link mechanism utilizing a parallel link and are balanced with a counterweight disposed on the other end portion of the retaining link mechanism, and thus these heavy medical optical devices can be retained at the desired spatial positions during microsurgery.
2. Description of Prior Art
In the fields of eneephalotomy and eardiosurgery, a technique of so-called microsurgery is employed, in which surgeries are performed under observation of the focuses using operating microscopes. Various types of stand apparatuses, for retaining heavy operating microscope and its auxiliary devices at the desired spatial positions, to be utilized in such microsurgeries have been proposed (e.g. U.S. Pat. No. 4,339,100). These stand apparatuses generally are of a balancing structure, in which a retaining link mechanism employing a parallel link is pivotally (tiltably) supported at the middle on a :frame, and an operating microscope is supported at one end portion of the retaining link mechanism with a counterweight for countervailing the weight of the operating microscope being supported on the other end portion of the retaining link mechanism relative to the pivot thereof.
As the position where the balancing type stand apparatus is set up, an optimum position in the operating room is selected depending on the content of the surgery to be carried out, and balance adjustment is performed at the selected position. In other words, while the optimum position around the operating table is specified by a doctor prior to surgery, the doctor himself is in a sterilized region, so that the actual operations of moving the stand apparatus to the position and setting it up are carried out by a nurse who does not participate in the surgery. Since auxiliary devices such as a side microscope for assistant doctors and a video camera are attached to the operating microscope, the nurse also moves the position of the counterweight to adjust the entire balance of the stand apparatus corresponding to the weight of these devices.
However, the operation of moving such heavy counterweight is a tremendous task and is also dangerous for the nurse who is in most cases a woman. Further, the balance adjusting operation takes too much time to be advantageously rendered for emergent surgery and the like.
What is most serious in the prior art stand apparatus is that the balance adjustment between the operating microscope and the counterweight is very difficult due to the structure of the stand apparatus itself. More specifically, in order to stop the operating microscope and the auxiliary devices at the desired spatial positions, the operating microscope must be balanced in the horizontal and vertical directions. However, since the prior art stand apparatus has only one counterweight, it has not always been easy to make secured balance adjustment in the horizontal and vertical directions in accordance with the weight on the operating microscope side which changes depending on the presence or absence of various auxiliary devices by means of the single counterweight.